The more they like sex, the more women like women

Being highly sexed changes men's and women's sexual orientation in startlingly different ways, a major academic study has concluded.

The research, conducted by Dr Richard Lippa, an internationally renowned sex expert at California State University, shows highly sexed women to be no less than 27 times more likely than men to become attracted to their own sex. The survey, of more than 3,500 people, is published in this month's Psychological Science. It showed that 0.3 per cent of men were attracted to their own sex, as opposed to 8 per cent of women.

For most women, a high sex drive increases their sexual attraction to both men and women. The opposite occurs in men, where a high sex drive simply exaggerates existing sexual orientation.

Dr Lippa told The Independent on Sunday: "Sexuality is more complex than we want to believe. It is more common for women to change their sexuality. My personal sense is that there are very few bisexual men, but there are significantly more bisexual women out there."

Researchers are finding evidence that there is a key biological difference at play between the sexes, rather than sociological factors alone.

This conclusion comes as no surprise to the television personality Rebecca Loos, a lifelong bisexual. "I do find that a lot of my female friends find women and men attractive, whether or not they happen to be in relationships with men," she says. "Most women I know have been with other women. Men and women are completely different when it comes to sex: for men it's a lot more physical."

As more women develop an open-minded attitude, celebrities are once again leading the way in bringing sexual orientation out of the closet. Madonna, Angelina Jolie and Saffron Burrows are among those famous for their relationships with both sexes. In the 1990s the columnist Julie Burchill had a much-publicised affair with the writer Charlotte Raven, whose brother she later married.

Data from last year's Sex Survey conducted by the BBC is expected to show twice as many bisexual women (6 per cent) as lesbians (3 per cent) in the UK. Numbers of women who had tried lesbian sex more than doubled between 1990 and 2000.

The TV sex therapist Tracey Cox says: "Bisexuality is going to be very interesting - something to watch, particularly with women. They've done experiments where they wire up people and get them to watch porn, woman on woman, man on man and hetero, and women were aroused by all three.

"Nearly all the sex therapists I know, if I ask what's the top fantasy for women, [will say] sleeping with another woman."